Why Does My Laundry Room Smell? Musty, Sewer and Rotten Egg Causes

A smelly laundry room usually comes from one of four things: a dried-out drain trap letting sewer gas in, a washer or dryer that stays damp, lint and soap buildup in the drain, or poor ventilation. Pour water into any unused drain first, then clean the washer door seal and check for leaks.

The smell tells you a lot. Sewage or rotten eggs points at the drain. Musty or sour points at moisture and mildew. Burning points at the dryer. Work through the steps below in order, from easiest to hardest.

Match the smell to the likely cause

• Sewer or rotten eggs: dry trap, clogged drain or venting problem
• Musty or damp: wet washer seal, mildew, a leak or no airflow
• Sour, like dirty clothes: biofilm inside the washer, or damp clothes left in the machine
• Burning or hot lint: a lint-clogged dryer or vent (see a smelly dryer)

1. Refill the drain trap

A trap is a U-shaped bend in the pipe that holds a little water. That water blocks sewer gas from rising. In a room you rarely use the drain, the water can evaporate and the gas gets through. This is the most common cause of a sewer smell in the laundry room.

1. Find the floor drain, laundry sink drain and the washer standpipe (the vertical pipe the washer hose goes into).
2. Pour a quart or more of water down each one that is not used often.
3. Add a spoonful of cooking oil to a floor drain. It floats on top and slows evaporation.
4. Wait a few hours and smell again.

If the smell goes away and comes back in a couple of weeks, repeat the water refill every month, or ask a plumber about a trap primer.

2. Clean the washer

A washer can smell even when the room is fine. Open the door and sniff the rubber seal and the detergent drawer.

1. Wipe the door seal, including inside the folds, with a cloth and hot water. Some guides use a mix of 1 cup liquid bleach to 1 gallon of hot water on the seal. Never mix bleach with other cleaners.
2. Pull out and rinse the detergent drawer.
3. Run an empty hot cycle with a washing machine cleaner.
4. Leave the door and drawer open after each wash.

Our full guide covers this in more detail: smelly washer fixes.

3. Look for leaks and damp spots

Moisture is the cause of most musty smells.

• Check both hoses behind the washer for drips or stains.
• Look under the washer and around the floor for soft or discolored spots.
• Feel the wall behind the machine and the baseboards.
• Look at the ceiling below the laundry room if it is upstairs.

A slow leak can run for months before you see it. If you find damp drywall or a soft floor, fix the leak first and dry the area completely. For leaks you cannot see, read our guide on how to find a concealed leak.

4. Clear lint and soap buildup

Lint, soap and hair collect in the drain line and on the back of the machines. This organic buildup can rot and smell.

• Vacuum behind and under the washer and dryer.
• Wipe the top and sides of both machines.
• Remove the lint screen and vacuum the slot.
• Clean the dryer vent if drying is slow. See how to clean a dryer vent.
• Pour hot water down the standpipe, then flush with a mild drain cleaner if the drain is slow.

5. Improve ventilation

A small laundry room with no window or fan holds humidity from every load. That moisture feeds mildew and can also pull water out of drain traps.

• Run the exhaust fan during and after laundry, if you have one.
• Open a window or the door when you can.
• Leave the washer door open to dry.
• Do not leave wet clothes in the washer or in a pile.
• If humidity stays high, a small dehumidifier can help. See dehumidifier running costs.

6. Check for gas smells

A rotten egg smell can also be natural gas, which has an added odor so people notice it. If you smell it near a gas dryer or water heater:

When to call a plumber

• The smell comes back after the trap is full and the washer is clean
• Other drains gurgle or drain slowly. See a sink that gurgles
• Water backs up from the floor drain or standpipe
• The smell is strong in more than one room. See a sewer smell throughout the house

These usually point to a clog or a vent problem in the main line, which needs a plumber and a drain camera.

Keep it from coming back

1. Run water into unused drains once a month.
2. Clean the washer seal and drawer every month.
3. Leave the washer open to dry.
4. Vacuum behind the machines every few months.
5. Run the vent fan during laundry.

Bottom line

Start with the drain trap, because it is free and takes a minute. Then clean the washer, check for leaks and fix the airflow. Call a plumber if the smell survives all four.